In the related art, a pattern detection device which detects a detection object in an image by pattern recognition has been known. The pattern detection device includes a discriminator generated by a discriminator generation device (pattern learning device).
On the other hand, in a pattern detection process, there is demand for detecting detection objects of various sizes in an image, for example, a distant detection object and a near detection object. In this case, in a typical detection process, detection objects of a plurality of sizes are detected by applying a single discriminator capable of detecting a detection object of a reference size to images of a plurality of sizes. In this process, the detection objects are detected by enlarging or reducing images according to the sizes of the detection objects and applying a discriminator of a reference size to the enlarged or reduced images.
For example, Non-Patent Literature 1 discloses an improved detection process compared to the above-described detection process. In this process, detection objects of a plurality of sizes are detected by applying a single discriminator to images of a plurality of sizes. However, in this process, detection objects of some sizes are detected by enlarging or reducing images according to the sizes of the detection objects and applying a discriminator of a reference size to the enlarged or reduced images, and detection objects of the remaining sizes are detected using a discriminator of a reference size after the above-described enlarged or reduced images are corrected.